Home Healthy Home HVAC Gimmicks vs. HVAC Mold Solutions—What Really Works and What Just Costs a Lot

HVAC Gimmicks vs. HVAC Mold Solutions—What Really Works and What Just Costs a Lot

by Catherine

The Post Your HVAC Contractor Doesn’t Want You to Read…

Are you trying to improve air quality in your home? Have you had an HVAC professional out to assess your current systems and to give you recommendations on possible HVAC mold solutions, add-ons, and enhancements? I’ll bet if you have, you are more confused now about what you should do than before they came. Am I right?

The reason I ask is because I get so many reader questions about various recommended HVAC “extras” and “solutions.” Many seem like viable proposals, but come with hefty price tags and not much explanation.

Fortunately for me, but unfortunately for those in HVAC sales, I have gained a crazy amount of knowledge in this area from personal exposure and experience during our mold nightmare and from experts in the fields of building science, indoor air quality, and environmental hygiene. When the mold issues in my home forced us to rip out and replace our entire HVAC system, ductwork, attic insulation, and ventilation systems, I threw myself into learning everything I could about our options and all of the possible solutions out there for our unique situation. Then, through working alongside the experts I mentioned and their technicians to make our home safe and livable again, I learned how to sort through the things that were worth the time and money and the things that just looked shiny and cool, but produced no significant home-health improvement for the expense. I guess you can say that I was given a peek behind the curtain of HVAC solutions from the perspective of a mold and indoor air quality expert.

Well, today, I am going to try to spread that knowledge. I will first list common HVAC recommendations that, in my opinion and experience, aren’t worth the money. Then, I will list HVAC and indoor air quality upgrades that I can whole-heartedly endorse. I will provide explanations and my experience with each, so that you can go into the conversation with as much inside knowledge as possible, especially if your main concern is mold.

Your HVAC System, Indoor Air Quality, and Mold

I probably don’t need to tell you why you should care about air quality and how your HVAC system affects the overall health of your home. But, just in case you need a refresher course, here is the quick and dirty:

The air you breathe is a more significant determiner of your overall health than your genetics. You may be born with stellar genes, but if you breathe in toxins, particulates, fungal and bacterial fragments, VOCs, dust, (all things that contaminate indoor air) in moderate to high concentrations, your health will suffer. In fact, indoor air pollution is more dangerous, because it is much more concentrated and contained. Outdoors, our bodies get a reprieve, because there is openness and fresh air, but inside, if the space we are in is toxic, there is no reprieve unless we physically leave. Also, naturally-occurring indoor contaminants, like mold, microbes, viruses and bacteria are sometimes odorless. Thus, we don’t know they exist or are problems for our health until we are negatively affected and get sick.  Add to this the fact that as a population, we are spending more and more time indoors (it is purported that most working Americans spend 92% of their time indoors) surrounded by all of these possible contaminants, and you quickly realize the importance of doing whatever you can to care for your indoor air quality and to make it as pure and as toxin free as possible.

These days, most of us live in homes with central HVAC (75% of Americans), and our indoor climates and the air circulating through them is controlled by these systems. To make our homes more pleasant and hospitable, we remove stale air and excess humidity with forced heating and air conditioning. This is a wonderful innovation, but it also comes with the limitation that we don’t want any of that forced heat or air to escape to the outside—we are paying for it, aren’t we?!! Thus, our homes are designed to be as sealed and as energy efficient as possible. These days, our homes are tight as ticks, with no air getting in or out. This is great for saving money and for keeping outdoor allergens at bay, but in terms of the health of the air inside your home, it is not so good. This is because anything, good, bad, or ugly is trapped inside and circulating in the air you are breathing.

Speaking of breathing, another thing trapped inside our tight homes is moisture. Moisture is released when we breathe, cook, bathe, shower, do laundry, fill a glass of water, use the air conditioning, open the door on a humid day, I could go on and on. Some people don’t consider indoor relative humidity an issue, because, in theory, it should be controlled by our HVAC systems. Air conditioned, circulating air, by design, reduces humidity and makes the indoors a hospitable and more comfortable place to be. Sometimes, though, there are conditions that actually prevent the conditioned air from keeping a home dry. Contributors to high indoor humidity include improperly designed and fitted HVAC systems (with systems that aren’t “right-sized” to cycle on and off in proper intervals, the HVAC cannot manage temperature or “condition the air” as it is supposed to), faulty window systems, moisture rising up into the home from a dirt crawlspace, improperly sealed or conditioned basement, kitchens, laundry rooms, and bathrooms that aren’t properly ventilated to the outside, and chimneys, attic stairs, and garages that aren’t sealed from the outdoors properly, just to name a few. With each fault in our home’s construction and/or HVAC design and efficiency, little introductions of moisture that aren’t subject to proper ventilation and quick drying can become condensation and food for mold, mildew, and rot.

Having to think about and consider all of these things can be quite overwhelming…

Enter the HVAC Professional.

Here is a person trained in indoor heating, air conditioning and ventilation systems. This should ideally include an understanding of the science behind the systems as well. HVAC professionals can design and install your system, clean the ducts, add systems like ionizers, UV antimicrobial lights, air purification units, air to heat exchangers, dehumidifiers, humidifiers, additional venting, etc. The list really could go on and on, and there really are some stellar products and systems to help you on the market. But, if your main concern is mold and its prevention, there are only a handful of these products and recommendations that will REALLY help you. Also, and a point that is often ignored, is the fact that the best things that you can do to improve your HVAC system are ONLY effective when they go hand-in-hand with some very basic concepts and techniques that target microbes (like mold and bacteria) specifically and what creates them in the first place—moisture and an organic food source. If the products or systems being sold to you don’t address these main concepts, you really shouldn’t spend your money on them, because the chances are high that they aren’t going to benefit your health. Right? Right.

Let’s Get Started.

Rather than over-complicate things, I am going to get right down to business, and in bullet-point fashion, first address the most popular HVAC solutions that I don’t feel are worth the spend and why. Then, I will offer you some better solutions that address your whole home and will not only aid your systems, but can prevent mold from being a problem. I won’t be able to touch on everything, but hope this will give you enough of a foundation to make more informed decisions in the future.

(Note: I have already written some pretty extensive posts about HVAC systems and have another post about choosing and installing an HVAC system in a new home for air quality and mold mitigation. If you are interested in revisiting any of those topics, I encourage you to click on the links above and explore further. Also important to note is that if your home has a moisture problem, it needs to be addressed first.)  

HVAC “Solutions” that (In My Opinion) Are NOT Worth the Money:

  • UV Lights – Cleaning your home’s air isn’t as simple as sticking a UV light in your HVAC system. To be killed or neutralized, microorganisms must be exposed to the right kind of light for the right amount of time. A UV system’s effectiveness in a given situation depends on lamp wavelength and intensity, number of UV lamps, lamp position, etc. Also, there are two types of HVAC UV light systems used: coil sterilization and air sterilization. Coil sterilization is the most common, but least effective as the UV light is installed near the evaporator coil, where it is supposed to shine constantly to prevent mold and bacteria from forming on or near the coil. The idea is that less mold and microbes on your coil means less of those things in your air. There is an obvious flaw, because the light cannot reach all sides of the coil and air passes over and around the light at a velocity where the light cannot effectively keep up with and kill all microbes and fungus. Air sterilization systems are installed in the return air duct and turn on when the heating or cooling system runs. It is designed to purify the air passing through the duct and reduce the build-up of contaminates on your HVAC components. The problem with this design is that it doesn’t address moisture or the fact that UV lamps lose power over time and become ineffective, even when they are still producing light. For the large expense, these systems just aren’t able to make a significant difference in air quality or to solve a mold problem that isn’t confined to the coil or HVAC handler.


  • Whole Home Humidifiers – When families have allergies, often whole-home humidification systems are recommended to soothe sinus and throat dryness. I cannot yell in a post, so I will do my best to simulate that here—DO NOT INSTALL A HUMIDIFIER ON YOUR HVAC SYSTEM!!!!! There are so many potential problems with these systems and the negatives, in terms of mold and bacteria growth, far outweigh the potential allergy help that moisture in the air can provide. (Note: If you desire moisture in your air, purchase a steam humidifier. I have a more in-depth post on that HERE.) For one, if not installed properly, so that they drain completely, humidifiers can pool water inside your system. This water will sit with any dust, or on your humidifier filter, and grow mold. Then, that mold will be blowing in the air throughout your home. (This is what happened in our home. It is a nightmare that I am intimately acquainted with.) Humidifiers also introduce moisture to your ducts and to the interior of your home. Any moisture that reaches organic material, like insulation, dust, drywall, fabric, can grow mold. Finally, most people do not change the filters or thoroughly clean their humidification systems with antimicrobials and antifungals and dry them completely after use. Unless this is done, they will always grow mold. You do not need this problem.


  • Duct Cleaning – While this sounds like a great idea, few companies know how to do this correctly. Unless the ducts are completely sealed from the rest of your home during vacuuming and cleaning, some of what is being cleaned and sucked out is also going directly into your air. I have actually spoken with many people whose health worsened after having their ducts cleaned! As a matter of fact, if done incorrectly, duct cleaning will actually make the health of your home and your indoor air quality much worse. In fact, the EPA doesn’t even endorse it as a way to better your air quality or to address mold, particularly because there are no conclusive studies that show any real health benefits from doing it. Further, if you have a mold problem or visible mold in your ducts, cleaning them with a duct cleaning method will NOT eliminate it. This is because, 1) duct cleaning does not address the CAUSE of the mold—usually excess moisture in your home or in your HVAC system, 2) duct cleaning will not eradicate mold in your HVAC system or ductwork—if you have a problem, simply vacuuming out your ducts and cleaning your registers is not going to take care of it, and 3) in order to clean your HVAC system, more than the ducts need to be addressed—cleaning of the air handler, registers, grilles, fans, motors, housings, and coils of the HVAC system would all have to be included and extremely through. Some companies offer this, but use harsh chemicals or steam shot through the ductwork (hello, moisture!!!) to do it. The chemicals then get into your air supply and toxins are spread throughout your home. If steam is used, there is moisture in your ducts (especially if you have flexible ducts) that then can grow mold. Finally, and this is a big one for me, the dangers of cross contamination. Most people having their ducts cleaned are doing so because of smells in their home, infestations in their ducts, dirty ducts, or suspected mold. All of the equipment used in their homes is now coming into your home to clean your ducts. The spread of mold, bacteria, and mycotoxins is a very real and underappreciated threat. You are working hard to keep your home healthy, so do not jeopardize this with duct cleaning equipment that could be contaminated.
  • Ionizers – This is one that I have gotten a lot of questions about lately. Ionizers are marketed as air cleaning devices that are installed on your HVAC system to release negative ions through the air ducts to disinfect the air by attaching to spores or dust to ultimately neutralize bad smells. They are also supposed to reduce dust levels in your home. (In doing so, the dust and mold must still be removed with a HEPA filter that is part of the ionizer or with a HEPA vacuum when they collect or fall to the floor.) I know it sounds wonderful, but this is extremely problematic for health in an indoor environment as the ionization process produces ozone. Ozone has been determined to create breathing problems for some people and can damage lung tissue. Also, according to the U.S. Environmental Protection Agency, ionizers perform less effectively than HEPA filters or whole house electrostatic air cleaners in terms of removing dust, tobacco smoke, pollen and fungal spores from the air. In my opinion, it is just not worth it for your health to take the chance of having high levels of ozone in your home, even if it means potentially cleaner air. Further, in many of the indoor air quality studies that have been done on ionizers vs. air filtration, ionizers perform much less effectively when it comes to mold, because they do not control moisture or effectively capture spores and/or organic matter from the air. Some people are drawn in by the idea of actually “killing” the mold and the bacteria with the ozone generated by the ionizer. I say that you shouldn’t be fooled by the hype, because the amount of ozone that would need to be generated throughout your home to kill a problematic mold issue would likely make you very sick first.

HVAC Solutions That Are (In My Experience and Opinion) Worth EVERY Penny:

  • Having your HVAC Units Checked and Serviced 2 times a Year by a Professional HVAC Technician – I cannot stress this enough. In almost every scientific study I have ever read concerning air quality, properly maintained and serviced HVAC units, when paired with high quality Merv 11 or higher filters (I will get to that in a minute) that are replaced every 3-4 months is the BEST recipe for reducing allergens in your home. Most people do not have their HVAC system regularly serviced. During service, your indoor and outdoor fans and units are checked for leaks, outdoor units are cleaned of debris, refrigerant lines are checked, condensate drains are cleaned, coils are cleaned, systems are calibrated, and the controls are checked.Some companies even do more, like check ducts for leaks. The point is that regular maintenance ensures that someone is looking over your systems to make sure that they are working properly and efficiently. This saves you money in the long run, because your systems stay tuned and your filters stay clean. It also saves your health and expenses associated with it. Oftentimes, technicians are even the first ones to spot a potential mold problem. When this occurs, your money has been even more well spent, because the sooner you find and fix the problem, the less chance it has of spreading throughout your home and making you sick.


  • Using Merv 11 or Higher Filters on your HVAC Unit – The quality of your HVAC filters is extremely important. You have to use filters that actually trap particles and mold spores. Flimsy filters that are not pleated or filters that are not changed every 3-4 months aren’t doing anything positive for your air quality. Your filter’s MERV Rating is a good way to help judge its effectiveness. MERV means Minimum Efficiency Reporting Value which was developed by the American Society of Heating, Refrigeration and Air Conditioner Engineers – ASHRAE. MERV values vary from 1 to 16. The higher the MERV value, the more efficient the filter will be in trapping airborne particles. Another consideration is air flow through your HVAC system. Leaving a dirty air filter in place or using a filter that is too restrictive may result in low air flow and possibly cause the system to malfunction. Merv 11 and higher filters are more expensive, but they actually FILTER the air in your home. This will decrease dust, mold, bacteria, smells, smoke, dust musts, and the spread of viruses.


  • Whole House Dehumidification – If there is one thing that controls the air quality in your home, it is moisture. In my opinion, moisture is king. Thus, controlling moisture is the name of the game if you intend on controlling mold growth.

    (There is also recent air quality testing that shows that VOC levels drop when indoor humidity is low.) Without moisture, you cannot have mold. What better way to control moisture in your entire home than to install a whole house dehumidification system? That way, you can control your ambient moisture levels from your thermostat. If you decide to make this kind of investment (with installation, one dehumidification unit will cost around $2,500—you need one unit per floor or for each HVAC system) you can set your indoor humidity below 50% and feel more secure in the knowledge that the dehumidifier is running to prevent moisture, condensation, and humidity that can lead to mold growth inside your HVAC system and your home. I will also make the pitch that whole house dehumidification actually saves you money in the long run, because when humidity is controlled, your comfort level rises inside your house. This means that in the summer, you will be comfortable at higher temperatures, and in the winter, you will need less humidity control and less heat. It is a win-win in my opinion. (Note: We have Honeywell Whole House Dehumidifiers. The other system I recommend is Aprilaire.)


  • Whole Home Air Purification – This may seem like an extravagance, but you can get solid systems at very reasonable prices. Air purifiers attached to an air handler typically provide better clean air distribution than stand-alone units. Additionally, they keep central heating and cooling equipment clean and running efficiently. They also have the ability to filter outside air before it enters an occupied area. Finally, these devices produce less noise, require less maintenance and are more cost effective for larger areas than stand-alone units. Whole house air cleaners can cost from $1,000 to $5,000. Most whole home filters don’t need to be changed as often as traditional HVAC filters, filter smaller particles than regular filtration alone, and do more to combat bacteria and viruses. They are definitely something to consider, if you are able to spend the money. If you cannot afford these systems, having multiple stand-alone air purifiers strategically placed will do the job. (Brands I recommend for stand-alone units are Molekule, Air Oasis, and IQ Air. HERE is a post I did on Molekule.)


  • Smooth Metal Ductwork – I know that ductwork is not glamorous, but if your house has flex duct, a good investment is swapping it out for metal ductwork. Flex duct is cheaper, but traps dust, dirt, debris, bugs, and moisture. As you can imagine, when all of these things are combined in pleated ducts, mold grows. Then, to add insult to injury, flex duct cannot be cleaned, but must be replaced. Smooth metal ducts to not tend to trap dust, dirt, moisture, etc. They are also easy to clean and to wipe down if needed. Another plus is that metal ducts do not have fiberglass insulation inside. Flex duct degrades over time, and the fiberglass insulation becomes exposed. Then, particles and small shards of glass can blow throughout the air in your home. When these are inhaled, they can damage the sinus walls. Not good. Totally worth the investment to get rid of it.


  • Right-Sized and Exterior-Vented Bathroom and Kitchen Fans and Dryer Vents – Spending money on correct ventilation is money well spent. If your bathrooms, kitchen and laundry room are not properly vented to the outside of your home, or if your fans are not sized correctly for the space to remove the moisture efficiently, you can have a mold problem. Having a professional come out to size the fans, to design the ductwork, so that the fans move the moisture outside of your home, and to install everything correctly is worth it. Making sure that this done right reduces indoor humidity and reduces the chance that the moisture from those places is being improperly routed into a wall cavity, basement, garage, or attic where it can lead to a huge mold problem. Even though the practice of venting bathrooms to the attic is not to code, builders still do it. So, even with a new home, this needs to be checked and corrected, if applicable. (I have a more in-depth post on this topic HERE.)


  • Sanitizer Fogger and EC3 Mold Solution Concentrate – I know this doesn’t seem like a HVAC-specific recommendation, but it is actually a very powerful tool for the air quality inside your home. Purchasing a fogger and using it regularly to fog indoors significantly reduces (down to zero in my experience—Go HERE to read that post and to see my mold plate tests) mold counts. If you use the fogger throughout your home regularly to control mold levels, your filtration system doesn’t have to work as hard to physically take the spores out of the air. It also takes time for mold to gain a foothold between fogging session. The foggers are extremely efficient with the EC3 and a bottle will last a long time. It literally takes minutes to fog a room. If you combine this action with the other items above it, you can have great indoor air quality at a reasonable price.


  • Overhead Fans – Yes, I know, fans are not a part of your HVAC system, but they can be an integral part of cooling, drying, and ventilating your home. I am a huge fan of ceiling fans. See what I did there? We put ceiling fans in all of our bedrooms and in our den and family rooms, because they constantly keep the air moving. Installing ceiling fans is also helpful in reducing your power bill, because if you know some simple hacks, you can run your HVAC less. Here they are: In the summer, ceiling fans should rotate counterclockwise to push cool air down to the floor. The cool air evaporates perspiration and creates a wind chill effect, which makes you feel cooler without affecting the room temperature. In the winter, ceiling fans should rotate clockwise at a low speed to pull cool air up. The gentle updraft pushes warm air, which naturally rises to the ceiling, down along the walls and back the floor.
Do you have comments or feedback on any HVAC or indoor air quality improvements that have made a significant positive impact on your health? I would love to hear from you! Comment or write to me at catherine@moldfreeliving.com.



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Mike Murphy - 2:05 am

This is great information and I did not want to place anything in my HVAC because I do not always run it in the summer or the winter. I wanted something that would work on a consistent basis, not just passive as many of the systems are. I saw an MSNBC segment about a company that had the technology approved by the FDA that was inspired by NASA that was tested and killed 99.9 % of the SARS and Covid 2 virus in the air and on the surface. I researched it more and it was the best idea I bought. It came with a 30 money-back guarantee, and since it qualified as a PPE I will get a tax deduction for the full cost of the unit. I called my HVAC person and told him if he knew about it and he didn’t so I sent him the website so he can provide it for his clients as a better choice and an affordable option. Protecting my family was my 1# reason I bought it. Im not a fan of some companies using fear to market something that will cost me more than the system initially cost me and NOT be effective.


Sheri Mowery - 12:09 pm

Thanks, Catherine, for the tips. We moved to our new home and are about to hear estimates back from our HVAC pro on these upgrades.The things you suggested were the things we were looking into. What do you think about shower dryers? We had those installed in our last house. They dry your shower within an hour or so to decrease the chance of growing mold. Also, I noticed you had an Aprilaire whole house purifier.We had those in our last house too. My HVAC guy also recommended an IQ air whole house purifier. Do you have any opinion on those?

Catherine - 4:15 am

Hi, Sheri,

Shower dryers are awesome! Just make sure they are paired with right-sized bathroom fans to remove the humidity to the outside. I wish we had an IQ Air. They are the BEST. We love our Aprilaire, but if I could do it again, I’d go IQ. I’m a totally convert with all of their products, because I haven’t found any air purifiers that work as well as theirs. Good luck with your new home! I am so happy for you!


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